V O L U M E 26, NO. 1 2 , D E C E M B E R 1 9 5 4
2001
point and the relative volatility was derived from the expression,
'
'a = where y is the mole fraction of di-2-ethylhexyl 4 1 - Y)' phthalate in the vapor and z is the mole fraction of di-2-ethylhexyl phthalate in the distilland. The calculated plate efficiency, n, is entered in the last column of the tables and was derived from the relationship n = ' C Y / C Y where CY = 3.47, the value determined by Hickman and Trevoy (6, 10) for the relative volatility of a mixture of di-2-ethylhexyl phthalate and di-2-ethylhexyl sebacate projertively distilled in a unit act a t 140' C. The observed values for n , with one exception, are all slightly greater than 1. This divprgence from unity probably represents a measure of slightly prolonged vapor-liquid contact brought about by the constricted opening in the barrel through which the vapors must pass to the condenser. ACKNOWLEDGMEKT
The authors are greatly indebted to C. F. Plummer for technical assistance, to J. H. Beebe and Paul Dolken for aid in the design of metal parts, to Boyer Clauson for the mechanical drawings, and to Richard Crook and Frank Rejc for the photographic work. LITERATURE CITED
Biehler, R. M., Hickman, K. C. D., and Perry, E. S., ANAL. CHEM.,21, 638 (1949). Breger, I. A., Ibid., 20, 980 (1948). Gilson, A. R., Chemistry & I n d u s t r y , 1950, 739. Hickman, K. C. D., Chem. Revs., 34, 51 (1944). Hickman, K. C. D., Znd. E n g . Chem., 44, 1892 (1952). Hickman, K. C. D., and Trevoy, D. J., Ibid., 44, 1903 (1952). Matchett, J. R., and Levine, J., IND.EXG.CHEM.,ANAL.ED., 15, 296 (1943).
Smith, C. C., and Matalon, R., Nature, 165, 613 (1950). Taylor. J. K.. J. Research AVuTatZ.Bur. Standards, 37, 173 (1946). Trevoy, D. J., I n d . E n g . Chem., 44, 1888 (1952).
cluding a cooling coil and bath, thermostatic bath, and viscometer and bath. Ruh, Conklin, and Curran (3) used a threebath arrangement with a bimetallic regulator. Haul and Theron (2) achieved good regulation using a bath surrounded by a cold reservoir with a heater regulated by a platinum resistance controller. The Zeitfuchs bath has only one cold reservoir, and regulation is achieved by intermittent circulation of the bath liquid through this cold reservoir. Only a single controller is required, and the bath can be cooled to the desired temperature rapidly. A schematic drawing of the bath is shown in Figure 1. The bath chamber is a 2.5-gallon, clear Dewar flask (American Thermos Bottle Co., Norwich, Conn., Catalog KO. 63403) insulated a t the top, bottom and partially around the circumference, with space left to view the viscometer tubes. In the bath chamber are a small centrifugal pump and stirrer on a common shaft driven by an induction-type electric motor mounted above the bath chamber. The pump circulates the bath liquid through a cooling coil immersed in an adjacent 1gallon Dewar flask which is filled with an acetone-carbon dioxide coolant. The pump also helps stir the bath. Regulation is achieved by a bimetallic regulator which, operating through a relay, opens and closes a solenoid valve in the line through which the bath liquid goes to the cooling coil. A throttling valve in this line permits rapid cooling of the bath. To operate the viscosity bath, carbon dioxide is placed in the coolant flask, and the throttling valve is opened fully. As the bath approaches the desired temperature the throttling valve is closed until only a small amount of liquid is being circulated and the final adjustment of the regulator is made. -4bout 30 minutes is required to cool the bath from room temperature to -55" C. The acetone in the viscosity bath must be kept reasonably dry or ice will collect in the solenoid valve and prevent it from closing completely. Normally rhanging the acetone weekly is sufficient to prevent this from happening. PERFORMANCE OF BATH
Zeitfuchs l o w Temperature Viscosity Bath Julian F. Johnson, California Research Corp., Richmond, Calif.
4
temperature viscosity bath has been in use for a number of years in these laboratories. It has been very satisfactory because of its simplicity, accuracy, small space requirements, and low initial cost. Similar baths have been described in the literature, but the Zeitfuchs bath is somewhat simpler. The bath of Baldeschwieler and Wlcox ( 1 ) has three parts, in-
-
LOW
The temperature of the bath is measured by a Speedomax recording resistance thermometer based on that designed by Stull (4). The temperature cycles about +0.02" to 0.03' C. about the mean value in a symmetrical manner. The mean temperature stays constant to &0.0lo to 0.02" C. for an hour or longer. The regulator is susceptible to thermal and mechanical shock, and the temperature should be checked after viscometers are inserted or removed. As there is a temperature gradient in the top 2 inches of the bath, viscometers must be located a t least 2 inches below the surface. The simple regulator is used because it is easily adjustable and gives satisfactory regulation. LITERATURE CITED (1) Baldeschwieler. E. L., and Wilcox, L. Z., IND.ENO.CHEY.,ASAL. ED.,11,221 (1939). (2) Haul, R. -4.W., arid Theron, J . J., J . Sci. Instr., 28, 236 (1951). (3) Ruh. E. L., Conklin. G. E., and Curran, ,J. E., IND.Exo. CHmi., SAL. ED..17, 451 (1945). ( 4 ) Stull, D. R., Ibid., 18,234 (1946).
Ultraviolet Irradiation for Air-Interrupted Spark Sources J. T. Rozsa and N. A. Grondin, National Spectrographic laboratories, Inc., L
Cleveland, Ohio
ultraviolet irradiation of interrupter gaps [Balz, G., KaiT ser, H., and Koch, P. H., Acta, 2,92-8 (1941)] is prevalent for spectrographic alternating current spark light HE
Spectrochim.
ACETONE COz BATH
il
w 2 k G A L . CLEAR DEWAR
Schematic Drawing of Bath
sources of the feussner type. Simpson [Simpson, S. F., J . O p t . SOC. Amer., 35, 40-2 (1945)l has demonstrated that the synchronization of small induction motors with applied voltage is often difficult because of their sensitivity to phase shifting and periodicity and that irradiation of the interrupted gap improves the uniformity of breakdown time of this gap. No such reasoning would be applicable to the air-interrupted type of inter-
